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Re: Philosophy: Seismic Design Standards and Performance Based Seismic Design

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I agree with Dennis Wish's statements in his January 19, 2000, email message 
on the Subject matter, in particular, the wording:  "I often wondered if we, 
as a professional community, know enough about natural disasters to stick our 
necks out to define just how well a structure will perform.  Had we started 
to advertise the idea that our codes were performance based before the 
Northridge earthquake occurred, would we have been surprised to find 
ourselves embroiled in numerous lawsuits for the damage that occurred?"

In July 1996, I wrote a letter, which was published in the SEAONC Newsletter 
and copies of this letter were posted, at least twice, on the SEAOSC List 
Service with the Subject: "And The Buildings Will Not Even Catch a Cold."   
In this letter, I attempted to point out the possible professional legal 
liabilities that would go along with the "implied warranties" that could be 
inferred with the use of  performance based seismic design.

In the 1999 SEAOC Blue Book is an Appendix I, Tentative Guidelines for 
Performance Based-Seismic Engineering" written by the SEAOC Ad Hoc 
Subcommittee, Robert Bachman, Chair. and et al.    I was a member of this Ad 
Hoc Subcommittee and was successful in providing the printed wording  in 
Section 1A-1.4, Limitations, page 368, and Section 1B-1.5, Statement of 
Limited Reliability, page 392, pointing out "However, there is no guarantee 
that the design performance objective will actually be achieved." and "It 
must be recognized that the reliability of PBSE is limited and that design 
performance objectives can not be achieved with certainty."

I am attempting to get similar wording in the ASCE/FEMA 273 and ASCE/FEMA 310 
Standards, which are under development. 

I have been lead to believe that FEMA  resisted inclusion of wording similar 
to the above 1997 Blue Book wording in FEMA 273, October 1997..  The 
strongest wording the authors of FEMA 273 could get in FEMA 273, Section 1.1, 
Purpose was:  "An engineer can use this document to help a building owner 
select seismic protection criteria when the owner's risk reduction efforts 
are purely voluntary.  The engineer can also use the document for the design 
and analysis of seismic rehabilitation projects.  HOWEVER, THIS DOCUMENT 
SHOULD NOT BE CONSIDERED TO BE A DESIGN MANUAL, TEXTBOOK, OR HANDBOOK."  
(Emphasis added.)

In fairness, FEMA did allow the wording buried in FEMA 273, Section 1.3.4, 
Technical Content, in the middle of a very long paragraph, which reads: 
"Compliance with the Guidelines should therefore not be considered a 
guarantee of the specified performance."   In my judgment, this long 
paragraph should have its own section heading, such as Section 1.3.5 
,"Limitations" or "Statement of Limited Reliability" instead of burying the 
above statement in the middle of a long paragraph where it probably will be 
overlooked.

Hopefully, the public will not be lead to believe that if the provisions of  
FEMA 273, ASCE/FEMA 273 and ASCE/FEMA 310 are followed "Their buildings will 
not even catch a cold."

By copy of this subject email message to the original authors of FEMA 273 and 
present authors of ASCE/FEMA 273 and ASCE/FEMA 310, I respectfully bring to 
their attention some suggestions on how these documents can be improved and 
hopefully, attempt to minimize the professional legal liability that goes 
with the use of performance-based seismic design. 



Frank E. McClure   January 20, 2000